Cryogenic fluids, e.g. liquid helium, are often used as refrigerants. For example, they may be used to cool certain missile subsystems, such as telescopes and infrared detection apparatus. In this application, the liquid is injected through a valve into a tank inside the missile just before firing. Since missiles are typically used in dangerous, life-threatening situations which require a swift and accurate response, it is imperative that the liquid charging process be speedy and exact. Additionally, to ensure the missile's proper operation, it is important to prevent contaminants from entering the system.
The general concept of pushing a male bayonet-type injector member against a spring-biased valve member for filling purposes is not new. However, prior injector or valve mechanisms employing this principle are not well-suited for missile and similar applications. They are either too cumbersome or have a complex locking system, either of which can slow down the filling process. Also, conventional such valves do not have mechanisms for preventing contaminants, such as dust or insects, from entering the valves and interfering with the proper operation of the valves and/or contaminating the liquid flowing through the valves. Additionally, in some prior valves, not enough attention has been paid to minimizing turbulent flow of the cryogenic liquid with the result that excessive evaporation of the liquid occurs in those valves.